cmd/compile: use | in the most repetitive mips64 rules
cmd/compile: use | in the most repetitive mips64 rules

For now, limited to the most repetitive rules that are also short and
simple, so that we can have a substantial conciseness win without
compromising rules readability.

Ran rulegen, no change in the actual compiler code (as expected).

Change-Id: Ia74acc389cd8310eb7fe8f927171fa3d292d2a86
Reviewed-on: https://go-review.googlesource.com/95797
Reviewed-by: Giovanni Bajo <387225cd66f97dc812a00599dbc5b6544a73295c@develer.com>

Cofyc/go,josharian/go,Cofyc/go,akutz/go,CAFxX/go,cloudflare/go,Cofyc/go,golang/go,cloudflare/go,josharian/go,josharian/go,codestation/go,cloudflare/go,CAFxX/go,akutz/go,akutz/go,nawawi/go,codestation/go,golang/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,cloudflare/go,akutz/go,josharian/go,codestation/go,nawawi/go,codestation/go,CAFxX/go,josharian/go,codestation/go,Cofyc/go,akutz/go,nawawi/go,golang/go,cloudflare/go,golang/go,akutz/go,nawawi/go,josharian/go,Cofyc/go,cloudflare/go,akutz/go,CAFxX/go,golang/go,josharian/go,CAFxX/go,CAFxX/go,nawawi/go,golang/go,codestation/go,codestation/go,cloudflare/go,Cofyc/go,CAFxX/go,josharian/go,Cofyc/go,nawawi/go,akutz/go,codestation/go,golang/go,Cofyc/go,golang/go